Determination of the liquid-phase speciation in the MDEA-H2O-CO2 system

AbstractAqueous solutions of alkanolamines are commonly used in CO2 capture processes. To describe these complex processes rigorous mass transfer models are needed, in which all mass transfer, kinetics and thermodynamics are incorporated correctly. To improve the quality of the thermodynamic models, not only commonly used P-α (CO2 partial pressure versus CO2 liquid loading) experimental data, but also liquid phase speciation data are important. Speciation data of amine-H2O-CO2 data are very scarce in literature. In this work speciation data of MDEA-H2O-CO2 have been determined experimentally with a Fourier Transform Infra-Red spectrometer (FTIR) at ambient temperature. After several calibration lines were prepared, the speciation of this system was determined online in the FTIR. The experimental data presented in this work were well in line with speciation from open literature

Desmopressin lyophilisate for the treatment of central diabetes insipidus : first experience in very young infants

INTRODUCTION: In neonates and small infants, early diagnosis of central diabetes insipidus (CDI) and treatment with desmopressin in low doses (avoiding severe hypo- or hypernatremia) are important to prevent associated high morbidity and mortality in this particular age group. CASE PRESENTATION: We described pharmacokinetic and pharmacodynamic results of the use of recently launched oral desmopressin lyophilisate (Minirin Melt®) in two infants with CDI, diagnosed at the age of 12 and 62 days, respectively. We observed that a starting dose of 60 μg of Minirin Melt® in the first case resulted in a pharmacokinetic profile largely exceeding the reference frame observed in children with nocturnal enuresis, while a dose of 15 μg in the second case resulted in acceptable concentrations. After initial dose adjustments, administration of sublingual lyophilisate resulted in rather stable serum sodium concentrations. CONCLUSIONS: Using Minirin Melt® in infants with CDI appears to be effective, easy to use and well tolerated

The effect of aqueous organic solvents on the dissociation constants and thermodynamic properties of alkanolamines

The dissociation constants of protonated monoethanolamine and N-methyldiethanolamine have been determined in methanol-water, ethanol-water, and t-butanol-water solvents. The alcohol mole fractions were ranging from 0.2 to 0.95 and the temperatures from 283 to 323 K, 283 to 333 K, and at 298.15 K, respective to the different solvents. The experimental results are reported with the standard state thermodynamic properties. The basic strength of the protonated alkanolamine decreases with decreasing dielectric constant and increasing temperature of the solvent. By using the dissociation constants of the alkanolamines in pure water, it is shown that a Born treatment alone is not able to estimate the dissociation constants when the composition of the solvent is changed to an aqueous organic mixture. (C) 2009 Elsevier B.V. All rights reserved

Influence of temperature on the kinetics absorption of carbon dioxide in aqueous of enzyme catalysed MDEA solutions

In the present work the absorption of carbon dioxide in 1000 mol m(-3) N-methyldiethanolamine (MDEA) solutions with and without enzyme has been studied in a stirred cell reactor in the temperature range 278-343 K and enzyme concentrations ranging from 0 to 1600 gm(-3). During this study a new type of carbonic anhydrase has been tested: the evolved tetrameric enzyme GS6-046. The kinetic data from the new enzyme has been compared to the kinetic data obtained with the thermostable CA mutant 5X and the new enzyme showed a faster kinetics towards the CO2 hydration in combination with MDEA. The experimental kinetic data from the evolved CA at the temperatures 278, 288 and 313 K resulted in a temperature dependent equation for the enzymatic rate constant K-H2O*. In the temperature range 278-313 K, this equation predicts k(H2O)* within an accuracy of 30%. However, at 343 K the measured k(H2O)* is significantly overestimated. (C) 2016 Elsevier Ltd. All rights reserved